It's like verbal diarrhea but with data! It often happens that you're looking for something (googling it perhaps) and you're hit with a barrage of data which might as well be in Chinese because you don't understand it anyway! And as you struggle with the reams and reams of endless information, you wonder if there is a pill you could take to make it all go away. Datarrhea!
The professor is obsessed with graphs, he's got a severe case of datarrhea.